For a long time, hydraulic actuators have been used in various systems and devices in which very considerable forces are required in very confined spaces. In modern commercial aircraft, too, hydraulic actuators are used at several positions, for example for moving control surfaces which due to the great dynamic pressure at high flight speeds are subjected to very considerable forces. When an aircraft is on the ground, cargo doors may be operated by hydraulic actuators in order to open or close a cargo space.
In larger commercial aircraft, which comprise a correspondingly large cargo space and thus large cargo doors, it may, at times, be observed that doors that are being opened tend to overshoot when the hydraulic actuator used reaches an end stop. This is due to the fact that the hydraulic actuator moves at full speed against the end stop, which in the state of the art occasionally is elastic, within certain limits, by means of a spring. However, since a larger cargo door is associated with relatively great inertia and since the lever travel of the hydraulic actuator used to open the cargo door is comparatively short, overshooting of the cargo door is induced when the end stop is reached, which overshooting represents a considerable load acting on the structure of the cargo door and of the cargo door frame, as well as on the bearing arrangement of both the cargo door and the hydraulic actuator.
In view of the foregoing, it may therefore be at least one object of the invention to reduce or entirely eliminate the above-mentioned disadvantage. In particular, it may be considered to be at least one object of the invention to propose a hydraulic actuator that is able to move larger objects from an initial position to an end position, and to prevent overshooting or subsequent oscillation when the end position has been reached. In addition, other objects, desirable features, and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.